Valley treated a sun drenched Butlin Road crowd to their best home win of the season, as they cruised to victory against relegation-fighting opposition.
A Justin Marsden double had given Town a half-time lead, with David Kolodynski matching his feat after the break before Caine Elliott rounded off the scoring with Rugby's fifth.
Jamal Clarke returned at centre-half in the only change to the hosts' starting line-up from the previous weekend's home win over Godmanchester.
Despite their lowly position, Biggleswade started the game confidently enough, and Jemale McKenzie's free-kick from twenty five yards which was deflected wide for a corner represented the game's first sighter at goal.
The visitors' early brightness was extinguished though, when Kolodynski bamboozled his marker on the right hand side before laying up Marsden to steer the ball into the bottom corner of the net on fifteen minutes.
Having broken the deadlock, Town went on to dominate the remainder of the half, with Elliott soon putting his free-kick into the arms of United keeper Michael Hudson and Edwin Ahenkorah blazing over the target after another assist from Kolodynski.
Marsden should have made it two-nil when he helped the ball over after Hudson could only parry Kolodynski's well-struck effort, but Valley's veteran player-assistant manager made amends shortly after when he curled a fine strike past Hudson after Harry Eden had cut the ball back across to him.
Chances for further Rugby goals continued to flow, with a Barry Fitzharris shot deflected wide and the lively Madundo Semahimbo finding the side netting with his effort.
Ahenkorah tested Hudson from distance, with the keeper forced into palming up the strike onto his crossbar, and then Semahimbo and Clarke got in each other's way when a corner caused problems for the Biggleswade defence.
The visitors were almost handed a lifeline on the eve of half-time though, when Eden's attempted header back towards Ash Bodycote left the Town keeper scrambling, but fortunately the ball just bounced marginally wide of the goal.
Charlie Black curled his shot the wrong side of the target, as the away side came out from the tunnel with renewed purpose, but Kolodynski's low calm finish after Elliott had stolen possession on the edge of the United box on 53 minutes removed any doubt as to the destination of the points.
Three minutes later Kolodynski was adding another - his 250th goal for the club - by tapping in Luke English's cross at close range.
Ahenkorah blazed one over on the turn, before Elliott burst through the middle of a by-now disheartened visitors defence to confidently stroke home Rugby's fifth.
The closest Biggleswade came to consolation saw Bodycote pull off a neat low save to sub Taylor Rhiney's strike, whilst Semahimbo missed out on what would have been a deserved goal of his own when Hudson tipped away his curling effort.
As the game wound down, Hudson comfortably caught a Semahimbo free-kick and Eden also blazed over, with Markel Cousins taking advantage of a rare lapse of concentration in Town's defence late-on, but he lifted his ultimate shot over the bar.
Valley Line-up: Bodycote; English (J Thomas), Eden, Summerfield, Clarke; Fitzharris, Marsden (Shaw), Elliott (Lock); Ahenkorah, Semahimbo, Kolodynski. Subs not used: Recci, Francis. Booked: None.
Biggleswade line-up: Hudson, Ampadu, Jones, Inskip, McKenzie, Gauge, Keane, Irish, Black, Andrews, Cousins. Subs: Puig-Valis, Hunt, El-Ouahabi, Rhiney.