Weatherald, 24, compiled a handy half-century in his customary position at the top of the order alongside new Redbacks rookie Henry Hunt.
He was eventually dismissed for 56 from 83 balls, combining with experienced teammate Tom Cooper (40) in an 80-run stand through the middle overs of the match.
Emerging allrounder Tom Andrews chipped in from the lower order and finished not out on 28 as the squad notched 9/195 after 50 overs.
Paceman Agar then took two wickets inside the opening eight overs of Queensland’s innings with the Bulls teetering on 4/45 in reply.
The 22-year-old claimed three wickets and bowled a maiden for figures of 3/43 from his nine overs, while Luke Robins (1/36) and Ben Pengelley (1/22) also earned breakthroughs.
Andrews and Lloyd Pope showed tenacity in the field to force run outs in the latter stages of Queensland’s chase in what proved a competitive clash.
But Bulls opener Matt Renshaw batted through Queensland’s innings to notch 101 and steer his side to the target total in 41.3 overs with just two wickets in hand.
The two teams will play a second practice match on Thursday at the same venue.
SA v QLD Practice Match – Redbacks’ top performers
Jake Weatherald 56 (83)
Tom Cooper 40 (67)
Wes Agar 3/43