The former will contest the RFU Junior Vase final against South Molton, from Devon, and Wath Upon Dearne’s opponents in the RFU Senior Vase final will be Saltash, from Cornwall.
Old Otliensians’ head coach Kris Stafford said the support from within the town of Otley has been fantastic.
“The whole club is excited for Sunday and it is a great achievement for the players,” said Stafford.
“We are over the moon with the support we are getting from the whole town and we can’t wait to put on a performance they can all be proud about.”
He added: “We have a strong squad from one to 22, which is a huge bonus, and due to that I am confident that we will bring the trophy back to Otley.”
Old Otliensians beat Eccleshall 28-12 in their semi-final in March to claim a place in the Twickenham showdown.
They had earned a last-four place by beating Wallsend, West Hartlepool TDS Old Boys and Ramsey.
South Molton saw off Chipstead 12-10 in their semi-final.
Wath Upon Dearne did well to negotiate a tough semi-final against Cornish opponents St Ives, who at the time were unbeaten in their league, coming out 29-7 winners.
Tomorrow’s opponents Saltash beat Old Cranleighans 31-15 in the other last-four tie.
Wath last visited Twickenham in 2012 when they were defeated 31-22 by Somerset club Wells. Manager Steve Corns says they want to erase the memory of that defeat by lifting the Senior Vase trophy tomorrow.
He said: “We have beaten the best in the North West and also in the Midlands, which shows our strength, and we hope to impress the 500 supporters coming to London.”
The road to the final for Wath Upon Dearne was exceptionally tough.
Having beaten North Shields 59-14 they were then drawn against the North West champions Winnington Park, from Cheshire.
But Wath managed what, on paper, appeared a tough game with great aplomb, triumphing 30-5.