Tasmania 4 for 168 (McDermott 70) beat Queensland 164 (Meredith 5-26) by six wickets
Meredith took two wickets in his first spell and three in the second after Tasmania captain Jordan Silk put Queensland in at Brisbane's Allan Border Field.
The hosts were skittled for 164 off 44.1 overs and Tasmania reached their target with 18.4 overs to spare to earn a second bonus point from as many games. Queensland have started the competition with two losses.
Openers McDermott (70 off 83) and Caleb Jewell (43 off 37) put on 94 from 15.3 overs, their second big stand in as many games following 198 against South Australia and effectively scuppered Queensland's hopes of defending their modest total.
Australian T20 and ODI representative McDermott struck ten fours and a six in a typically fluent and powerful innings following his 71 against the Redbacks, who Jewell made 126 against.
Tasmania lost 3 for 1 in eight balls with Michael Neser dismissing both Silk and Mac Wright for a duck in the same over. Jake Doran and Beau Webster steered them home, with the latter ending the match with a six.
Tasmania's pace quartet extracted movement from the wicket and were backed up by some high quality catching and ground fielding, and left-arm spinner Tom Andrews.
Meredith, who represented Australia in ODI and T20I formats last year, returned career-best limited overs figures. The 25-year-old quick bowled five maidens across his two spells, troubling the Bulls with his length, line, movement and pace.
Tom Rogers followed up his five wicket haul in Wednesday's win over South Australia, with 3 for 32 off 8.1 overs.
Mark Steketee, batting at No. 9, top-scored for Queensland with 35 not out off 36 balls, notching his highest domestic one-day competition total.
Queensland couldn't muster a partnership any higher than 18 until their ninth-wicket pair of Steketee and Xavier Bartlett added 48 to rescue them from 8 for 95.
So effective was the Tasmania attack it took 22 overs before a Queensland batter reached 20 and seven of the top eight were dismissed for under 14.
Max Bryant (26 off 40) was the only specialist batter to make a start. Test stars Usman Khawaja and Marnus Labuschagne, who was lbw to Meredith, were dismissed for 13 and 10 respectively.