B737-800
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 131
Communication Breakdown; Confusion; Distraction; Situational Awareness; Time Pressure
Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Took Evasive Action
Aircraft; Environment - Non Weather Related; Procedure
Not late-not in a hurry.  Right at pushback we got the runway and departure change.  During engine start First Officer grabbed the performance computer and began programming changes.  Then we got a pre-taxi ATC call about construction issue near our gate. While stopped; I decided to go through the runway taxi and departure changes and went into departure takeoff mode. Out of sequence now; I inadvertently overlooked the Before Taxi checklist before taxiing.  During taxi we both knew we were out of sequence; so I said I wanted to re-review the departure and performance data.  That's when the First Officer noticed the flaps at 0 and instinctively grabbed the handle and set to five.  So flaps were reset on the move.  We then re-ran the Before Taxi checklist and reconfirmed all configure/takeoff and departure items. I should not have allowed First Officer to begin performance computer changes during pushback. I should have waited until after the Before Taxi checklist was completed prior to addressing the clearance changes. I normally am very sequence oriented but I let the combination of clearances and extra ATC chatter and performance programming knock me out of sequence.
A B737-800 crew became distracted during pushback and engine start by ATC changing the runway and departure. While recalculating performance data the First Officer failed to lower flaps which the crew discovered when the Taxi Checklist was reviewed during taxi.